1. Field of the Invention
The present invention relates to a three-dimensional (3D) display device capable of viewing three-dimensional images without using special glasses, and more particularly, to a three-dimensional display device so adapted that an uncomfortable feeling in replacing a right eye image and a left eye image on a screen in correspondence to the position of the head of a viewer can be eliminated.
2. Description of the Prior Art
Conventional examples of a device for displaying 3D images without using special glasses include one so adapted that a parallax barrier or a lenticulated lens is arranged on the side of a viewer on a display screen of a display panel such as a liquid crystal display (LCD) panel, so that a 3D image can be viewed by separating light from a right eye image and light from a left eye image which are alternately displayed for each vertical line on the display screen from each other.
There is also a device for displaying a 3D image without using special glasses by separate incidence of light for left eye and light for right eye on a display panel of a transmission type such as an LCD panel.
In the above-mentioned 3D display device, an optimum viewing position is set, as shown in FIG. 26. That is, the optimum viewing position on which a right eye image and a left eye image are converged is set to a position spaced an optimum viewing distance D apart from a 3D display device 200. In the optimum viewing distance D and predetermined ranges ahead of and behind the distance D, diamond-shaped regions R where the right eye image can be viewed and diamond-shaped regions L where the left eye image can be viewed alternately exist for each distance between the eyes E of a viewer 2 as shown in FIG. 27. In a position a where the right eye 2R and the left eye 2L of the viewer 2 respectively exist in the region R and the region L, normal 3D images can be viewed. This is equivalent to the case where the center of both eyes of a viewer exist in the position shown in diamond-shaped region a of FIG. 26. On the contrary, in a position b where the right eye 2R and the left eye 2L of the viewer 2 respectively exist in the region L and the region R, no 3D images can be viewed due to reversed view. This is equivalent to the case where the center of both eyes of a viewer exist in the position shown in diamond-shaped region b of FIG. 26.
In order to enlarge a region where 3D images can be viewed, therefore, a 3D display device 200, which is provided with a sensor 201 for sensing the position of the head of the viewer 2, and image replacement means for replacing a right eye image and a left eye image on a display panel of the 3D display device 200 when the sensor 201 senses that the head of the viewer 2 is in a reversed view position, as shown in FIGS. 27 and 28, for example, has been proposed (see, Japanese Patent Application No. 7-253888, for example).
This is equivalent to the case where the center of both eyes of a viewer exist in the position shown in diamond-shaped region a of FIG. 26. FIG. 27 illustrates a state where the head of the viewer 2 is in a position where normal 3D images can be viewed. The right eye 2R is positioned in a region R where a right eye image can be viewed, and the left eye 2L is positioned in a region L where a left eye image can be viewed. FIG. 28 illustrates a state where the head of the viewer 2 is in a position where no 3D images can be viewed due to reversed view in the conventional example. This is equivalent to the case where the center of both eyes of a viewer exist in the position shown in diamond-shaped region b of FIG. 26. As shown in FIG. 28. A right eye image and a left eye image on the display panel of the 3D display device 200 are replaced with each other, whereby the region R where the right eye 2R can view the right eye image and the region L where the right eye 2R can view the left eye image are replaced with each other. As a result, the right eye 2R is positioned in the region R where the right eye image can be viewed and the left eye 2L is positioned in the region L where the left eye image can be viewed, so that normal 3D images can be viewed.
As described in the foregoing, in the 3D display device 200 so adapted that the right eye image and the left eye image which are displayed on the display panel are replaced with each other, when the eyes of the viewer are shifted to a reversed view position, it is possible for the viewer to view proper images by replacing the right and left images. However, a crosstalk region or a black region exists between the region R where the right eye image can be viewed and the region L where the left eye image can be viewed, as shown in FIG. 29, until the eyes of the viewer 2 are moved from the normal view position to the reversed view position. The crosstalk region or the black region reaches the eyes of the viewer 2 while the right eye image and the left type image are replaced with each other, whereby the viewer 2 views a blurred double-image or a moire-shaped image and has an uncomfortable feeling in a position where the crosstalk region or the black region reaches the eyes of the viewer 2. In the present invention, the position where the crosstalk region or the black region reaches the eyes of the viewer 2 so that the viewer 2 views a blurred image or a moire-shaped image is generically named a moire position. A moire region mainly exist in the position spaced approximately one half of the distance between the eyes of the viewer apart from the center of the normal view position. This is the position that the head of the viewer is in when the viewer's head is spaced approximately one-fourth to approximately three-fourths of the distance between the eyes of the viewer apart from the center of the normal view position.